Fine you want a more general example.
In the Athenian democracy. To become a citizen you had to complete military training, which would have made you 21 if I remember correctly, then you could join the assembly. To move from the assembly to the court you had to be over 10 years older than that because of the "Wisdom comes with age" philosophy.
So, statistically, at the absolute youngest, the Athenian court was made up of one year old skeletons.
To join the Spartan senate Gerousia as another example. You had to be over 60.
Anyway, as a field of science, statistics kind of suck. Because you have to have VERY detailed ones for them to be of importance. A general statistic is nigh useless.